The invention relates to an air bag for occupant restraint systems in motor vehicles, which air bab is automatically and rapidly inflated by a gas generator to form a balloon-like hollow body in the event of an accident. The air bag wall which is substantially nonpermeable to gas is reinforced in a central region facing the occupant and, on the inside of the air bag, is connected to catch straps in such a way that the air bag assumes a flattened, lenticular shape, with outlet possibilities for the gas produced by the gas generator.
Air bags of this type have already been used as a standard fitting in motor vehicles for a relatively long time and have proved to be expedient. It is important for a good protective effect that the air bag only remains inflated for a relatively short time and then becomes slack again. This avoids that the air bag, which has been inflated in the manner of a cushion, is substantially only elastically deformed upon impact of the occupant and thus hurls the occupant back after the impact with correspondingly great force.
An air bag of this type is known from German Patent Document DE 4,033,835 A1, whose shaping is influenced by catch straps in such a way that, in the inflated state, an approximately lenticular hollow body results. The construction of gas outflow apertures, whose presence is essential in order to allow slackening of the inflated air bag, is not explained in greater detail in this publication.
In this context, it is known from German Patent Document DE 4,031,325 A1 to arrange in an air bag an annular, gas-permeable zone which concentrically surrounds a central attachment region.
It has been established in practice that this type of construction of the air bag is not yet optimum in terms of simple producibility and good strength.
An object of the invention is therefore to provide an air bag of the type specified above, which can be produced in a simple manner and is distinguished by a high strength.
According to the invention, this object is achieved by the combination of the following features:
a) the wall of the air bag consists of fabric which is permeable for the gases of the gas generator within a kidney-shaped or crescent-shaped zone which is spaced away from the central region and is approximately concentric thereto; and PA1 b) the gas-permeable fabric is oriented in warp and weft at an angle of about 45.degree. to the warp and weft of the fabric forming the remaining wall of the air bag.
Due to the arrangement according to the invention, the gas-permeable fabric as well as the seams joining said fabric to the remaining air bag cover and the corresponding edge zones are loaded very evenly.
In particular, it is guaranteed that the catch straps attached as appropriate, on the inside central region of the air bag cover, are unable to exert any impermissibly large forces on the gas-permeable fabric.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.